Azeotropic distillation of paraffinhalogenated paraffin mixtures



United StatesPatent Ofiice 3,349,008 AZEOTRQPIC DISTILLATION F PARAFFIN- HALOGENATED PARAFFIN MIXTURES Van C. Vives, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Nov. 19, 1964, Ser. No. 412,455 11 Claims. (Cl. 203-60) ABSTRACT 0F THE DISCLOSURE Mixtures of parafiinic hydrocarbons and halogenated parafiins are separated into their component parts by adding an aZeotrope-forming material (entrainer). The paraffinic hydrocarbon is then removed by means of an azeotropic distillation leaving the halogenated paraffin as a product which is withdrawn. The azeotrope-forming material is selected from the group consisting of N,N-dimethylforrnamide, N,N-diethylformamide, N-methyl-N- ethylformamide, N,N dimethylacetamide, N,N diethylacetamide, acetonitrile, propionitrile, butyronitrile, amethylbutyronitrile, sacs dimethylpropionitrile, and aethylbutyronitrile. This separation process is particularly well suited for concentrating the halogenated parafiin component from a halogenation reaction prior to its introduction into an alkylation reaction.

This invention relates to azeotropic distillation separations. In another aspect this invention relates to an integrated process for the production of detergent alkylates.

Various chemical processes are being practiced in which halogenated parafiins are used as solvents and employed as intermediates in processes such as alkylation and hydrolysis. The parafiins are halogenated by various known methods. Several of the processes using halogenated paraflins operate more efficiently if the halogenated parafiins are separated from parafiinic hydrocarbons prior to their use. One such process is the production of detergent alkylate wherein an aromatic such as benzene is alkylated with monochloroalkanes. In this particular process it has been found that the polychlorides cause formation of heavy byproducts which rapidly reduce the life of the aluminum chloride alkylation catalyst. Cyclic hydrocarbons are also produced from the polychlorides, and these undesired products co-distill with the desired alkylate. Because of the adverse eifects of the polychloroalkanes in this process, the normal paraffins are chlorinated under conditions such that low conversions are obtained to reduce the formation of polychloroalkanes. If the alkyl chlorides are not separated from the parafiins prior to the .alkylation step, large amounts of unchlorinated parafiins are present during the alkylation step. The disadvantages, both technical and economic, of having the unchlorinated paraflins present during this alkylation are obvious to those skilled in this art. It is extremely difiicult and expensive to separate mixtures of halogenated paraffins from paraffins when their boiling points do not differ greatly. Mixtures of this type are frequently obtained when a paraflin feed stock containing molecules of consecutive carbon numbers and differing by a spread of more than 2 carbon atoms, for example a mixture of C C C and C paraffins, is subjected to halogenation.

Accordingly, an object of this invention is to provide a method for the separation of halogenated parafiins from mixtures with paraifinic hydrocarbons. Another object of this invention is to provide an improved integrated halogenation-separation-alkylation process for the production of detergent grade alkylate.

According to this invention an improved process is provided for the concentration of halogenated paraifins which comprises separating halogenated parafiins from mixtures with paraflinic hydrocarbons by azeotropic distillation with an entrainer selected from the group consisting of N,N dimethylformamide, N,N diethylformamide, N- methyl N ethylformamide, N,N dimethylacetamide, N,N diethylacetamide, N methyl N ethylacetamide, acetonitrile, propionitrile, butyronitrile, a methylbutyronitrile, 06,06 dimethylpropionitrile, and 0a ethylbutyronitrile.

In a specific embodiment of this invention an improved process is provided which comprises halogenating paraffinic hydrocarbons, separating and recovering the resulting halogenated paraffins by azeotropic distillation, and alkylating an aromatic hydrocarbon, such as benzene, with the recovered halogenated paraflins' The azeotropic distillation process of this invention is applicable for the separation of halogenated parafiins from par-affinic hydrocarbons. This invention is most applicable to the separation of halogenated parafiins containing 8 to 20 carbon atoms per molecule from parafiins with the same range of carbon atoms and more preferably of a range of 10 to 16 carbon atoms per molecule. The parafiins are halogenated by contacting them with a halogen, preferably chlorine and bromine, for about 5 to 30 minutes, preferably in the presence of ultraviolet light at a temperature of from about -20 to +40 0, a mole ratio of paraffin to halogen of from 3:1 to 10: 1, and a pressure from atmospheric up to about 500 p.s.i.a. The azeotropic distillation process for separating the halogenated parafiins is carried out at a temperature below that at which any decomposition of the haloparaflins occurs. Normally, this decomposition temperature will approximate C. Generally, the azeotropic distillation is carried out at a pressure below 750 mm. mercury absolute pressure. As will be shown in the examples, a pressure in the range of about 300 to 600 mm. mercury absolute is preferred to a very low pressure such as 5 to 10 mm. mercury absolute.

The optimum amount of entrainer for a given mixture can be determined by distilling a small amount of a specific n-paraflin-monochloroparafiin mixture with various amounts of a chosen entrainer. In this manner, one can use an entrainer/mixture ratio which will cause the retention of a minimum amount of entrainer in the kettle material. Generally, the weight ratio of entrainer/paraffin-chloroparaffin mixture will be in the range of 0.25:1 to 5:1.

The azeotropic distillation process of this invention is carried out in either a batch or continuous manner in any type distillation column as may be desired. The entrainer can be added to the process at various points in the system, or it may be premixed with the mixture to be separated, or a combination of such steps can be employed.

A particular utility for the concentrated halogenated paraifins produced by this invention is in the alkylation of suitable aromatics, such as benzene, toluene, xylene, naphthalene, biphenyl, phenanthrene, anthracene, pyrene, chrysene, ethylbenzene, and the like. In the alkylation of benzene for use as a detergent alkylate, the monochloroand monobromoalkanes are preferred.

The catalyst employed in the alkylation process can be any suitable alkylation catalyst, that is sulfuric acid, substantially anhydrous hydrogen fluoride, and a so-called Friedel-Crafts metal halide. Included among said Friedel- Crafts metal halides are those such as aluminum chloride, aluminum bromide, boron trifiuoride, and a halide of such metals as zinc, tin, arsenic, antimony, zirconium, berylium, titanium, iron and the like. These metal halide catalysts are especially effective when used in the form of complexes which are formed by interaction between the metal halide and hydrocarbons. A particularly desir- I.) able catalyst is a complex of hydrocarbon with aluminum chloride. An aluminum chloride-hydrocarbon complex catalyst can be prepared, for example, by contacting aluminum chloride with isobutane or other branched chain paraffius in the presence of olefins such as ethylene.

Such complexes normally contain about 55 to 65 percent by weight of aluminum chloride, the remainder being hydrocarbon.

Conditions employed in an alkylation process will depend somewhat upon the catalyst employed. When employing aluminum chloride-hydrocarbon pomplex catalyst, the alkylation will generally be carried out at a temperature within the range of 50 to 135 F. with a pressure sufficient to maintain liquid phase conditions. Flow rates of reactants should be maintained such that the residence time is Within the range of from about to about 30 minutes, preferably about to about 25 minutes, will be provided.

The mol ratio of 'armonatic hydrocarbon to halogenated hydrocarbons entering the alkylation process should be such as to furnish at least one mol-of aromatic hydrocarbon per gram atom of halogen on the halogenated hydrocarbonlt is preferred .to operate with an excess of aromatic hydrocarbon. Thus, the mol ratio of aromat-,

ic hydrocarbon to halogenated hydrocarbon is usually maintained within the range of 2:1 to 30:1, preferably 8:1 to 25:1. The volume ratio of catalyst used to the total halogenated paraffin in the process should be in the range of about 0.5:1 to 10:1, preferably about 2:1.

This invention will now be described more fully with reference to the accompanying drawing which shows a schematic flow diagram and apparatus representative of the invention.

A paraflin stream from a molecular sieve separation (not shown) is introduced into halogenation zone 2 through conduit 1. The halogen is introduced into zone 2 through conduit 3. The reactants are thoroughlycontacted inzone 2 and the resulting mixture is withdrawn through conduit 5 and introduced into distillation zone 6. Distillation zone 6 is preferably operated at subatmospheric pressures. When operated at subatmospheric pressures, vacuum can be supplied by conventional apparatus, e.g., a stream jet ejector mounted to draw. suction fromthe vapor space of an overhead accumulatonThe ejector, overhead condenser, overhead accumulator, or other well-known auxiliary equipment are not shown in this schematic drawing. Simultaneously, entrainer is introduced into zone'6 through conduit 7 below the feed entry 5 of the halogenated reactants. Alternatively, valves 4 in conduit 5 and 4a in conduit 5a can be switched so that the halogenation mixture from zone 2 can be admixed with the entrainer in conduit 7 prior to introduction into zone 6. An azeotrope of parafiin and entrainer is withdrawn from zone 6 through conduit 9 and introduced into washing zone 10a. In washing zone 10a this material is contacted with water to facilitate phase separation. Water is supplied to zone 10a throughconduitll. Water is introducedfrom conduit 11 directly into zone 10a through valve 812 and branch conduit 11a, or into conduit 9 entering zone 10a through valve 8b and branch conduit 11b, or simultaneously into both conduit 9 and zone 10a. The resulting mixture is withdrawn from zone 10a through conduit 9a and introduced into separation zone 1012. In separation zone 1012, a quiescent zone, the mixture separates into an upper paraflin phase and a lower water-entrainer phase. The parafiin phase is withdrawn from zone 10bthrough conduit and is suitable for recycle to. the parafiin' halogenation zone 2. The

water-entrainer phase is withdrawn through conduit 13' and passed to entrainer recovery zone 12. The bottoms from distillation zone 6, comprising haloparaflins and some entrainer, are removed through conduit 19 and introduced into washing zone 14. In washing zone 14a this material is contacted with water to facilitate phase separation. Water is supplied to zone 14a through conduit 11.

Water is introduced from conduit 11 directly into zone 14a through valve. and branch conduit 110, or into conduit 19 entering zone 14a through valve 8d and branch conduit 11d, or simultaneously into both conduit 19 and zone 14a. The resulting mixture is withdrawn from zone 14a through conduit 1% and introduced into separation zone 14b. In separation zone 14b, a quiescent zone, the mixture separates into an upper haloparaffin phase and a lower water-entrainer phase. The haloparafiinv phase from zone 14b is withdrawn through conduit 21 and in troduced into alkylation zone 16 for the manufacture of alkylates. Alternatively, the monochlorides and dichlorides can be separated, if desired, prior to introducing the monochlorides to thealkylation zone. The water-entrainer phase is withdrawn from conduits 13a and 13 and passed to entrainer recovery zone 12. In entrainer zone 12 any suitable separation means such as distillation is employed for the separation of entrainer and water. The recovered entrainer is then recycled via conduit 7 to distillation zone 6. The recovered water is fed to conduit 11. Makeup Water conduit 17 is provided for injection of makeup Water to conduit 11 as needed. When operating as a batch process, a halogenated parafiin storage vessel (not shown) will be used in conduit 5 and an entrainer storage vessel will be used in conduit 7. Alkylation catalyst is introduced to zone 16 through conduit 23. An aromatic hydrocarbon is introduced to zone 16 through conduit 25. Reaction mixture is removed from zone 16 through conduit 27. This mixture is passed to a recovery system (not shown) for separation of the alkylate, catalyst, and unreacted aromatic and halogenated parafiins.

The following specific examples will give a better understanding of the invention but-are not intended to limit the invention.

Example I A mixture comprising 51.1 grams of n-dodecane, 6.2 grams l-clorododecane, and 4.2 grams of 1,10-dichlorodecane was added to 79.1 grams of N,N-dimethylformamide (DMF) in a 250 ml. distillation pot. A flash distile lation was carried out at mm. Hg pressure, giving a distillate boiling at,82-88 C. Three 17 m1. fractions and one 30 ml. fraction were collected. The DMF from these fractions was separated and recycled to the distillation pot. Two of these fractions and the pot residue were analyzed by gas-liquid chromatography. The distillation was resumed until ml. more was taken overhead. Total liquid overhead was 231.8 ml. (208.6 grams), and of this 32 ml. (24.4 grams) was a hydrocarbon top layer, and the remainder a DMF bottom layer, including that recycled. During distillation, material as one phase distilled overhead, which when cooled to room temperature formed the parafiin and DMF phases.

The paraflin phase analyzed 3.1 weight percent DMF, 96.3 weight percent n-dodecane, and 0.6 weight percent l-chlor-ododecane by gas-liquid chromatography. After water. washing, the paraffin phase analyzed 99.4 weight percent n-dodecane and 0.6 weight percent l-chlorododecane. The DMF phase in the overhead receiver was analyzed by gas-liquid chromatography and found to contain 95.3 weight percent DMF, 4.6 weight percent ndodecane, and 0.1 weight percent l-chlorododecane.

After about 53 weight percent of the original mixture had been taken overhead, the pot residue was analyzed by gas-liquid chromatography and found to contain, after water washing to remove the DMF, 74.9 weight percent. I

n-dodecane, 18.5 weightpercent 1-cl1lorododecane,.and 6.6 weight percent 1,10-dichlorodecane.

Head Pren- B.P., 0. Analysis of Overhead sure, mm. Hg of Overhead 37 3.9 weight percent l-chlorododecane 96.1 weight percent n-dodecane 330 120 1.4 weight percent l chlorododecane 98.6 weight percent n-dodecane Along with the advantages shown from the above data and specific embodiments, the azeotropic distillation process of this invention provides a ready means for separating halogenated paraffins from paraffinic hydrocarbons. These materials cannot be readily separated by conventional distillation because of the relatively close boiling points of the materials to be separated. The following table shows the closeness of the boiling points of the constituents in the mixture to be separated.

BOILING POINT C.

Constituent mm Hg abs. 345 mm Hg abs.

Secondary chloronndecane Primary chlorodecane Secondary chlorododecane n Tridecane Primary chloroundecane The separation allows the paraflins to be recycled to a halogenation zone. When operating at low conversions in the halogenation zone for ultimate production of monohalides, a large amount of paraifins travels through unreacted, making the azeotropic distillation and separation and paraifin recycle desirable. Also, in the alkylation process, the removal of parafiins prior to alkylation avoids the problem of passing large amounts of inert material through the alkylation zone.

To one skilled in the art it will be evident that many variations and modifications of this invention can be practiced in view of the foregoing disclosure that will come within the spirit and scope of the invention.

I claim:

1. The process of separating a mixture comprising haloparaflins and parafiins, which comprises:

introducing said mixture into a distillation zone;

distilling said mixture with an entrainer selected from the group consisting of N,N-dimethylformamide, N, N-diethylformamide, N-methyl-N-ethyl formarnide, N,N-dimethylacetamide, N,N-diethylacetamide, N- methyl-N-ethylacetamide, acetonitrile, propionitrile, butyronitrile, a-methylbutyronitrile, one dimethylpropionitrile, and u-ethylbutyronitrile, said entrainer being added to said zone along with said mixture, to form an azeotrope with said paraffinic hydrocarbon; withdrawing said azeotrope and entrainer as overhead; recovering a paratiin rich fraction from said overhead; withdrawing said haloparaffins as bottoms product; and recovering a haloparafiin rich fraction from said bottoms product.

2. The method according to claim 1 wherein said haloparafiin comprises l-chlorododecane, said paraflin comprises n-dodecane, and said entrainer comprises N,N-dimethylformamide.

6 3. The process of separating a mixture comprising haloparaffins and parafiins, which comprises:

introducing said mixture to a distillation zone; distilling said mixture with an entrainer selected from the group consisting of N,N-dimethylformamide, N, N-diethylformamide, N-methyl-N ethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N- methyl-N-ethylacetamide, acetonitrile, propionitrile, butyronitrile, ix-methylbutyronitrile, 00,0: dimethylpropionitrile, and a-ethylbutyronitrile, said entrainer being added to said zone at a point below a point at which said mixture is introduced, to form an azeotrope with said parafiinic hydrocarbons; withdrawing said azeotrope comprising said paraffin and entrainer as overhead; recovering a paraifin rich fraction from said overhead; withdrawing said haloparafiins as bottoms product;

and recovering a chloroparafiin rich fraction from said bottoms product. 4. The process of claim 3 wherein the hydrocarbons have 8 to 20 carbon atoms per molecule.

5. The process of claim 4 wherein the distillation is made at a pressure between 5 and 760 mm. mercury.

6. The process of separating a mixture comprising chloro-paraffins and paraflins, which comprises:

introducing said mixture into a distillation zone; distilling said mixture with an entrainer selected from the group consisting of N,N-dimethylformamide, N, N-diethylformamide, N-methyl-N ethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N- methyl-N-ethylacetamide, acetonitrile, propionitrile, butyronitrile, a-methylbutyronitrile, oc,a dimethylpropionitrile, and a-ethylbutyronitrile, said entrainer being added to said zone at a point below a point at which said mixture is introduced, to form an azeotrope with said parafiinic hydrocarbons; withdrawing said azeotrope comprising said parafiin and entrainer as overhead; recovering a paraflin rich fraction from said overhead; withdrawing said chloroparafiins as bottoms product;

and recovering a chloroparaflin rich fraction from said bottoms product. 7. The process of claim 6 wherein the hydrocarbons have 8 to 20 carbon atoms per molecule.

8. The process of claim 7 wherein the distillation is made at a pressure between 5 and 760 mm. mercury.

9. The process of claim 6 wherein the entrainer is N,N- dimethylformamide.

10. The process of separating a mixture comprising ndodecane and l-chlorododecane, which comprises:

introducing said mixture into a distillation zone; distilling said mixture with an entrainer selected from the group consisting of N,N-dimethylformamide, N, N-diethylformamide, N-methyl-N ethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N- methyl-N-ethylacetamide, acetonitrile, propionitrile, butyronitrile, a-methylbutyronitrile, oc,ot dimethylpropionitrile, and w-ethylbutyronitrile, said entrainer being added to said zone at a point below a point at which said mixture is introduced, to form an azeotrope with said paraifinic hydrocarbons; withdrawing said azeotrope comprising said n-dodecane and entrainer as overhead; recovering an n-dodecane rich fraction from said overhead; withdrawing said l-chlorododecane as bottoms products; and recovering a 1-chlorododecane rich fraction from said bottoms product. 11. The process of claim 12 wherein the entrainer is N, N-dimethylformamide.

(References on following page) References Cited I UNITED STATES PATENTS,

Tooke 203-60 Glazier et a1 203-60 Burch 203-60 Grekel et a1. 203-96 Fannin et a1 203-60 Taylor et:a1. 203-60 8 FOREIGN PATENTS NORMAN YUDKOFF, Primary Examiner.

DELBERT E. GANTZ, Examiner.

C, R. DAVIS, W. L. BASCOMB, Assistant Examiners" UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,349,008 October 24, 1967 Van C. Vives It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 66, for "hydrocarbon" read hydrocarbons column 6, line 19, for "chloroparaffin" read haloparaffin line 72, for the claim reference numeral "12" read 10 Signed and sealed this 26th day of November 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr.

EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. THE PROCESS OF SEPARATING A MIXTURE COMPRISING HALOARAFFINS AND PARAFFINS, WHICH COMPRISES: INTRODUCING SAID MIXTURE INTO A DISTILLATION ZONE; DISTILLING SAID MIXTURE WITH AN ENTRAINER SELECTED FROM THE GROUP CONSISTING OF N,N-DIMETHYLFORMAMIDE, N, N-DIETHYLFORMAMIDE, N-METHYL-N-ETHYL - FORMAMIDE, N,N-DIMETHYLACETAMIDE, N,N-DIETHYLACETAMIDE, NMETHYL-N-ETHYLACETAMIDE, ACETONITRILE, PROPIONITRILE, BUTYRONITRILE, A-METHYLBUTYRONITRILE, A,A - DIMETHYLPROPIONITRILE, AND A-ETHYLBUTYRONITRILE, SAID ENTRAINER BEING ADDED TO SAID ZONE ALONG WITH SAID MIXTURE, TO FORM AN AZEOTROPE WITH SAID PARAFFINIC HYDROCARBON; WITHDRAWING SAID AZEOTROPE AND ENTRAINER AS OVERHEAD; RECOVERING A PARAFFIN RICH FRACTION FROM SAID OVERHEAD; WITHDRAWING SAID HALOPARAFFINS AS BOTTOMS PRODUCT; AND RECOVERING A HALOPARAFFIN RICH FRACTION FROM SAID BOTTOMS PRODUCT. 